title: Quantum of optical absorption in two-dimensional semiconductors.
abstract: The optical absorption properties of free-standing InAs nanomembranes of thicknesses ranging from 3 nm to 19 nm are investigated by Fourier transform infrared spectroscopy. Stepwise absorption at room temperature is observed, arising from the interband transitions between the subbands of 2D InAs nanomembranes. Interestingly, the absorptance associated with each step is measured to be ∼1.6%, independent of thickness of the membranes. The experimental results are consistent with the theoretically predicted absorptance quantum, AQ = πα/nc for each set of interband transitions in a 2D semiconductor, where α is the fine structure constant and nc is an optical local field correction factor. Absorptance quantization appears to be universal in 2D systems including III-V quantum wells and graphene.
authors.affiliation: Department of Electrical Engineering and Computer Sciences, University of California, Berkeley, CA 94720, USA.
authors.forename: Hui
authors.initials: H
authors.lastname: Fang
authors.forename: Hans A
authors.initials: HA
authors.lastname: Bechtel
authors.forename: Elena
authors.initials: E
authors.lastname: Plis
authors.forename: Michael C
authors.initials: MC
authors.lastname: Martin
authors.forename: Sanjay
authors.initials: S
authors.lastname: Krishna
authors.forename: Eli
authors.initials: E
authors.lastname: Yablonovitch
authors.forename: Ali
authors.initials: A
authors.lastname: Javey
mesh_terms: D000042:Absorption; D001152:Arsenicals / Q000737:chemistry*; D007204:Indium / Q000737:chemistry*; D008027:Light; D008956:Models, Chemical; D049329:Nanostructures / Q000737:chemistry*; D011789:Quantum Theory; D012666:Semiconductors; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D001152:Arsenicals; D007204:Indium; C076773:indium arsenide